Stabilized physical developers



United States Patent 3,390,998 STABILIZED PHYSICAL DEVELOPERS Roger M. Cole, Rochester, N. assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 4, 1965, Ser. No. 492,834 20 Claims. (Cl. 96-66.5)

ABSTRACT OF THE DISCLOSURE Stabilized photographic physical developers containing a superadditive combination of ionic surfactant and organic antifoggant.

This invention concerns physical developers for photographic images, and more particularly, physical developers stabilized with surface active agents. 7

The most common type of photographic development process is that wherein a sclution of chemical reducing agent is employed to reduce metal ions which make up the latent image-forming material. Such a process is termed chemical developmen since the developing solution does not contain any dissolved compounds of the reducible metal. In the case of a chemical developer for silver halide compounds, initially, there is no appreciable concentration of silver ions, although depending on the solvent activity of other components which make up the solution, some dissolved silver ion may be built up, partically after extended use.

It is known that photographic images can also be produced by means of a physical developer. Whereas chemi cal developers act on silver salts of the image-forming layer to form density in image areas, physical developers in principle contain dissolved silver salts as well as the silver halide developing agents. These have been described in H-ornsby Basic Photographic Chemistry, 1956, Fountain Press, London, England.

Physical developers have been used for producing silver images in ordinary photographic silver halide emulsion layers, which after exposure, have been first fixed to remove the silver halide and to leave only the initiating site for development.

Physical developers are inherently unstable, tend to darken and lose activity because of the interaction between the silver ion and the reducing agent present in the same solution. Means for increasing the stability of such solutions have been continually sought. One method of increasing the stability has been to decrease the concentration of the reagents. This has led to solutions of very low capacity (few images can be developed) and to a very retarded rate of development. Solutions having high activity and high capacity tend to show sludging, that is, to form a dark precipitate which decreases the activity and usefulness of the physical developer.

Some improvement in the stability of physical developers is obtained by the addition of various ionic surfactants as described in Jonker et al., U.S. Patent 3,157,- 502 incorporated herein by reference. Such surfactants include amines, sulfonates and the like. However, the resulting increase in stability is not enough to permit storage of the stabilized solutions for more than several hours and still maintain reasonably active development rate. Further, development with such solutions becomes less selective as the solution is used, that is, silver is deposited not only on image site, but also on background areas, container walls, rollers, etc. used in conjunction with the processing cycle.

It has been desirable to find a method of stabilizing physical developers which would enable active solutions to be kept for several months without serious deterioration and to increase the useful life of a used developer to several hours or days.

3,399,998 Patented July 2, 1968 I have found, that by adding to physical developers another agent along with an ionic surfactant, that I obtain a superadditive effect with respect to stability and other properties of the physical developer. The combination of the surfactant and the second agent produces a better effect than the sum of the two effects taken separately.

One object of this invention is to provide 'a stable physical developer solution of good developing activity having a useful life of from several hours to several days. Another object is to provide stable monobaths which in the unused state may be stored several months without sludge formation. An additional object is to improve the development selectivity of physical developers so that they will deposit metal only 'where there are active nuclei and not in other areas of the image forming layers.

The above objects are achieved by adding to physical developers a combination of ionic surfactants and water soluble organic compounds which includes those agents generally classed .as antifoggants.

For the purposes of this invention, physical developers may be defined as those developing solutions wherein substantially all of the metal for development is contained as a soluble reducible salt in the solution. A particular solution should contain at least 5X10 moles per liter of reducible metal (silver) salt before its initial use. This distinguishes physical developers from the developing solutions which are monobaths, since monobaths initially contain no reducible metal (silver) ion before use. After a monobath has been used many times for the development of silver halide layers, a considerable silver concentration may be built up in the monobath because of the solvent activity of the solution. My invention is also applicable to such solutions.

The physical developers which are useful in the invention must contain a reducible metal ion (silver) and one or more silver halide developing agents known in the art. The reducible metal ions may be any of those which can be reduced to the metal by any of the wellknown photographic developing agents. In conventional physical developer solutions, the reducible metal salt is a water soluble silver salt usually silver nitrate. However, other soluble silver salts may be used as Well as salts of metals such as copper, mercury, platinum, gold, palladium, etc.

The photographic developing agent may be a dihydroxy-benzene type or the like. Typical useful developers include hydroquinone, catechol, ascorbic acid, isoascorbic acid, pyrocatechol, gallic acid, gentistic acid, pyrogallol, etc. Paraphenylenediamine type silver halide developers may be used selected from those which are known inthe art. In addition, aminophenol types may be used such as p-methylaminophenol sulfate, o-a-mino' phenol, p-hydroxyphenylglycine, etc.

It will be appreciated that compounds known as auxiliary developers may be used also, such as the pyrazolidone type materials, and a combination may be used of more than one type of the various types referred to above as well as a combination of developers with auxiliary developing agents.

Various compounds may be included in the physical developer solution such as compounds intended to control the pH, particularly those used for buffering the solution, sulfite to improve the stability, a halogen salt, etc.

In a monobath, it is necessary to have a silver complexing agent present. Typical agents are silver complexing agents such as sodium thiosulfate and the like. The particular silver complexing agent may be selected from one or more of those known in the art as silver halide complexing agents.

Physical developers may be used wherever nuclei are present as sites for physical development. For instance,

these developers may be used to intensify chemically developed silver images, to develop light activated nuclei such as zinc oxide, zinc hydroxide, titanium dioxide, etc. They may also be used with systems wherein nuclei are treated with light-sensitive substances rendering the nuclei inactive as sites until exposed to light, as described in Gilman et al., US. Ser. No. 332,305, filed December 20, 1963, now US. Patent No. 3,330,- 658. In a related system the nuclei are rendered inactive by exposure to light as described in Hanson et al., US. Ser. No. 266,328, filed March 19, 1963, now US. Patent No. 3,320,064, and the active nucleiare developed using a physical developer.

Surfactants which are useful in stabilizing physical developers include ionic surfactants or surface-active substances which are adsorbed at the boundary surface of two phases. These are usually organic compounds which contain both one or more hydrophilic and one or more hydrophobic groups, which are bonded together either directly or, for example, by an ester, ether or amide bond. The hydrophobic groups may be, for example, aliphatic carbon chains having from 8 to 18 carbon atoms in contradistinction to the hydrophilic groups. The latter are therefore sometimes referred to as solubilizing or polar groups. These may be, for example, sulphonate 'or pyridinium groups.

The surfactants may further be defined as ionic surfactants, the hydrophilic group of which carries the Charge and which thus occur in the form of an anion, a cation or a Zwitterion. These are referred to as anion-active, cation-active and amphoteric surfactants, respectively. Non-ionic species, however, are ineffective.

The following surfactants are typical of those which may be used to stabilize physical developers.

Trade Name Composition Source NCH2 Amine 220 nitrate C17H33C -HNO Union Carbide 00.

N Hg

Hz-CHzOH NCH2 Amine O, Amine S CH (CH 11-0 Alrose Chem. Co.

III-CH2 for Amine O, n=16 Moi weight- 355 for Amine S, n=-16 M01 weight=360 R is a substituent having a comparatively low m0- leeular weight Areskap 100 CnH5-C0H2{8 I Monsanto Chemical Corp- SO Na Aresket s00 c6m our3{g&

Aresklene 400 C H C {E) fi D0.

Armae 12D 90% C H ,-,-NH -OH CO0H Armour & C0.

C14H2uNHz-CH3COOH Deodrant G 271 R CH -CH Atlas Powder.

N O (SO4C2H5 (Di H CH CH2 R=CieHsa, isHai, isHaa, Cia ss, CieHs'l and alkyl residues with 20-24 carbon atoms Deodraut G 251 01 E1 CH -CH Do.

N O (SO4C2H5) Cz H5 CH CH Dcsogen H Geigy.

CHQ CGHQ-(J" (CH2)1UCH3 (80 011;)

N (CH CHzCHzCHzN(CHz-CH2OH)2 Ethoduomene T/13 O H N Armour & C0.

CHz-CHzOH Fixanol C i (C5H5NHC1QHQ3)X (X=C1 or Br) Light dz C0.

CH CH Hya-mine 10X (CH3)30CHZ --CGH O 02114-0 C2H4N(CH3)2-CHz Imperial Chem. 111d.

H mom-H505 Lissapol C CH3(CH2) C=O(CH2)1CH SO4N-a Rolun and Haas.

It it or CH (CHz)1CHiCH-(CHz)r-GHzOH Imperial Chem. Industries.

SO4Na Sap-amine A C 7H3 C-NCzH-1N(CzH )2- 01330 O OH Ciba.

Ciba.

Spamine KW l. [C1BH37|J1TIC2H4N(CH3)3 4 3) Sufficient surfactant is used to increase the life of the developer at least 50% when compared to the life of an identical developer without the surfactant as described in US. 3,157,502.

In accordance with the invention I have made, the life of the surfactant stabilized developer may be further increased by the addition of photographic chemicals generally recognized as antifogging agents. The effect of such addition of both surfactant and antifogging agent produces stabilization beyond that expected from simple additivity.

Sufiicient antifoggant is used to increase the life of the surfactant-stabilized developer at least 50% when compared to the identical developer as described above which has been surfactant stabilized.

Organic reagents which are useful in our invention a e selected from those antifoggants which are customarily used for lowering fog in the photographic art. In general, my invention concerns antifoggants which are water dispersible organic compounds which form complexes with ionic silver, said complexes form a non-reducible layer which tends to insulate the metal nuclei and to prevent them from acting as catalytic centers for physical development. It is well known that inorganic salts, particularly bromides and iodides exhibit marked antifogging properties. My invention is not directed toward such inorganic salts, but is limited to organic compounds of the type to be described below.

As a further description of antifoggants, it has been indicated that they are compounds which form silver salts of solubility in the same range as or less than silver chloride. Antifoggants cover a varied group of compounds, many of which are listed in Mees, The Theory of the Photographic Process, page 679, 1954, and in Glafkides, Photographic Chemistry, volume I, 1958, beginning at page 374.

The following antifoggants are intended to be illustrative of those which may be used depending upon the surfactant and the physical developer:

(A) Cyclic amines, for example, diphenylamine and benzidine derivatives having at least two NH groups,

etc.

(B) Iminazoles, for example, 6 nitrobenziminazole, p-nitrobenziminazole, etc. Mercaptobenziminazole, for example, 2-thio 4 methyl 5 acetyliminazole, 3-allyl- Z-dimethyl-Z-thiohydantoine, etc.

(C) Triazoles, for example, benzotriazole, 5 methylbenzotriazole, p-nitro-4-azimidobenzene, etc.

(D) Tetrazoles, for example, l-phenyl 5 mercaptotetrazole, 5 phenyltetrazole, 5 (m-nitrophenyl)- tetrazole, etc. I

(E) Thiazoles, for example, 2 methylbenzthiazole, including the mcthiodide (or ethyl-p-toluenesulphonate) or 2 methyl-benzthiazole, 2 amino 4 methylthiazole, 2 diethylamino 4 methylthiazole, 2 aminothiazole- 5:4':5:6-quinoline, 2 thio 4 methyl and 2-thione-3- benzyl 4 methylthiazole, 2 benzylidenehydrazino-4- oxathiazoles, etc.

(F Mercaptobenzthiazoles, for example mercaptobenzthiazole, 2 methylmercaptobenzthiazole, N-ethyl mercaptobenzthiazole, N-benzyl mercaptobenzthiazole, etc.

(G) Oxazoles, for example,-2-hydroxybenzoxazole, 2- hydroxy -6-nitrobenzoxazole, etc.

(H) Thiosemicarbazides, for example, thiosemicarbazide, NH CSNHNH aldehyde-semicarbazones, etc.

(I) Pyrimidines, for example, 2-marcapto-4-methyl pyrimidine, 2 mercapto 4 methyl 6 hydroxypyrimidine, 2 mercapto 5 methyl 6 hydroxypyrimidine, 2 mercapto 3 allyl -4 methyl-G-hydroxypyrimidine, 2-mercapto-4:6 diaminopyrimidine, 2:6 dihydroxy-4z5- diarninopyrimidine, 4 methyl 2:6 dimercaptopyrimidine, 2 amino 4 hydroxypyrimidines, 2 mercapto- 4 hydroxy, halogenated hydroxypyrimidines, such as 5- chloro or bromo 2:6 dihydroxypyrimidine, thioderivatives of 2:6-dihydroxypyrimidine, etc.

(J) Thiazolidines, for example, derivatives of penicilline, the penicilloic, penicillic and penaldic acids and penilolaldehyde, 2 styryl 4 carboxythiazolidines, etc.

(K) Iodonium derivatives, for example, diphenyliodonium nitrate, 4-(2':4'-diiodophenoxy) quinaldinic acid, etc.

(L) Thiobarbituric acids, for example, thiobarbituric acids, phenyl-thiobarbituric acid, Z-hydroxylidine-thiobarbituric acid, 3 methoxy 4 hydroxybenzylidinethiobarbituric acid, etc.

(M) Benzene-sulphinic acids (N) Alaloids, for example, the hydrochlorides of quinine and quinidine, morpholine' derivatives such as phenylmorpholine, 2v aminothiazole 5:6:526 hydrocinchonidine and its derivatives, 2-picolic acid, etc.

(O) Thioanilides such as thioacetanilide, etc.

(P) Saccharin and pyrazoline derivatives.

(Q) Brominated fatty acids and acetylene dicarboxylic acids as their soluble salts.

(R) Protein degradation products: cysteine and histidine hydrochlorides.

(S) Compounds containing the SH group.

It will be appreciated that the antifoggants which can be used are directed to those which are compatible with the physical developer and with the surfactant or surfactants which are also present as stabilizing agents. For

example, those few antifoggants which produce in one way or another a precipitation with one of the constituents of the physical developer cannot be used.

In order to determine whether a given antifoggant is serviceable as a physical developer stabilizer under the conditions which prevail in the physical developer chosen, the following determination is made:

A portion (200 milliliters) of the complete physical developer is placed in a glass cell with an optical path of two inches. A SOO-watt lamp is placed on one side of the cell and a light meter on the other (length from lamp to meter is 12 inches). The solution is continuously agitated and the change in transmittance observed. When there is an eight-times decrease in transmittance, the sample is considered sludged. The time required for this degree of sludge is used to calculate the stabilization factor.

Four developers are used: (1) controlno preservative, (2) control with surfactant only, (3) control with antifoggant only, and (4) control with both. The stabilization factor is the time required for a stabilized developer to sludge divided by the time for the control developer to sludge. The superadditive stabilization factor is calculated by dividing the time for the control developer to sludge into the time for the developer to sludge when both surfactant and antifoggant are present. A superadditive effect is observed when the sum of the stabilization factors of the developer with surfactant alone and developer with antifoggant alone is less than the stabilization factor of the developer containing the surfactant and antifoggant in combination.

The following developers are illustrative of physical developers in general but other physical developers may be used to carry out the invention:

Water to make 1.0 liter.

Developer B The following examples showing the synergistic effect Part A: of the addition of both antifoggant and the surface active Water 4000 agent are intended to illustrate the invention but not to sodlum ulfite limit it in any way. 9 ISOaSCPrbatC'H2O In Table IA results are listed in the form whi h Dlbaslc potasslum phosphate illustrates the efiect of adding a series of antifoggants to Water to make 500.0 ml. d 1 f d PH=8 O a eve oper containing common sur a ctant a ditives.

Part B: I In Table 1B, the results are presented in the form which Water 400.0 illustrates the effectof adding a ser es of surfactants to si chloride "g" 1.8 a developer containing common antifoggant additives. Sodium sulfite g 9,6 The data in Table II shows similar superadditive effect Water to make 500.0 ml.

with Developer B which is at significantly lower pH. TABLE IA.EXAMPLES WITH DEVELOPER A Individual Superadditive Surfactant Antifoggant Stabilization Stabilization Factors Factors Control None 1 1 Hyaniine 10X do 5 None 3-meroapto-1,2,4-ti1azo1e 4 Hyarnine 10X do t 120 None i 2- (methylthio)jbenzothiazole 6. 1 Hyamine 10X. .do 450 0 2-niercapto-5-methylsulfon-amidobenzoxazole 38 Hyamine l0X .do t t 150 None o-tolidine 4. 2 Hyamine 10X do 11 one 5-nitrobenzim1dazole 1. 2 Hyamine 10X... do i 5-Iuethylbenzotriazole. 1. 3 .i- Hyamine 10X o None 2-methylbenzothiazole. 1i 6 Hyamine 10X do 8 None t Salieylaldehyde semlcarbazone 1. 6 Hyamine 10X do t t 11 one B-mercaptopurine. 12 Hyamine 10X one Hyamine 10X.

one

Armac 12D None Arman 12D N one Ar mac 12D N Areskap None Areskap 100 N Areskap 100. Amine 0- TAB LE IB Individual Stabihzation Factors Super-additive Stabilization Factors Antifoggant Surfactant 116phenyl-S-mercaptotetrazole- None Hyamine 10X l-phenyl-5-mercaptotetrazole None 1-phenyl-5-mercaptotetrazole TABLE IL-EXAMPLES WITH DEVELOPER B Individual Superadditive Stabilization Stabilization Factors Factors Surfactant Antifoggant Hyamine 10X None Armae 12D Deodorant G251- Areskap 100--.. None None o-Mercaptobenzoie acid. Areskap 100 .do

The stabilization factors for each of the combinations shown above indicate the marked improvement in stability of the physical developing solutions when both surfactant and antifoggant are present.

It is well known that surface active agents play an important role in suspending particulate matter in solution. In the photographic art it is likewise well known that antifoggants affect the developability of some silver halide grains such that the greater development differentiation is possible between exposed and unexposed grains. However, it is unexpected that the combination of such additives would produce such striking effects on the stability of solutions which contain both reducible silver and reducing agent. Having discovered this efiect, we can postulate that the antifoggant acts on any centers for development, to prevent further growth in size while the surfactant acts on such centers to prevent coagulation and precipitation. However, such a simple interpretation is not adequate to explain the magnitude of the stabilization factor, for the combined action, over the anticipated additive effect of the individual components.

Having described the improved stability of solutions prepared according to the method of my invention, the following example is given to demonstrate the usefulness of such a stabilized solution in the development of a photographic image. The particular example below illustrates post-fixation development, but it will be recognized by those skilled in the art that my invention applies to all those other processes wherein physical development is used for amplification of an existing image on active nuclei sites.

A sample of Kodak Fine Grain Positive film was exposed and developed in D-76 at 68 F. for 7 minutes as a control.

The same exposure was made to another sample and then fixed in a solution containing 50 g./l. hypo and 50 g./l. Na CO for 3 minutes. It was rinsed 30 sec. in water, then developed in the physical developer A for minutes to give the same average contrast as the control.

The images developed in the physical developer were of higher quality (had higher actuance) than those developed in the control.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant and at least one organic antifoggant, said antifoggant being present in an amount suflicient to increase the life of the developer at least 50% when compared to the life of an identical developer containing the surfactant.

2. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent selected from the group consisting of N-methylaminophenol sulfate, pyrogallol, N,N-dimethyl-pphenylenediamine, phenyl-1-pyrazolidone-3, hydroquinone, pyrocatechol, o-aminophenol, ascorbic acid, N-p-hydroxyphenylglycine and N-N-diethyl-p-phenylenediarnine, at least one ionic surfactant and at least one organic antifoggant, said antifoggant being present in an amount suflicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

3'. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant and an iminazole antifoggant, said antifoggant being present in an amount sufiicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

4. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt .reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant and a triazole antifoggant, said antifoggant being present in an amount sufiicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

5. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant and a tetrazole antifoggant, said antifoggant being present in an amount sufficient to increase the life of the developer at least 50% when compared to the life of an identical developer containing said surfactant.

6. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant and a thiazole antifoggant, said antifoggant being present in an amount sufiicient to increase the life of the developer at least 50% when compared to the life of an identical developer containing said surfactant.

7. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant and an oxazole antifoggant, said antifoggant being present in an amount sufiicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

8. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant, and a semicarbazide antifoggant, said antifoggant being present in an amount sufficient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

9. A stabilized photographic physical developer comprising an aqueous solution of a Water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant, and a pyrimidine antifoggant, said antifoggant being present in an amount sufficient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

10. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant, and a thiazolidine antifoggant, said antifoggant being present in an amount sufficient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

11. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant, and an iodonium antifoggant, said antifog gant being present in an amount suflicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

12. A stabilized photographic physical developer com prising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, an ionic surfactant and a thiobarbituric acid antifoggant, said antifoggant being present in an amount sufiicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

13. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant, and a benzene-sulphinic acid antifoggant, said antifoggant being present in an amount sufiicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

14. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant and an alkaloid antifoggant, said antifoggant being present in an amount sufficient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

15. A stabilized photographic physical developer comprising an aqueous solution of water soluble metal salt reducible to metal, a photographic reducing agent, for reducing said metal salt to metal, at least one ionic surfactant, and a thioanilide antifoggant, said antifoggant being present in an amount sutficient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

16. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant, and a pyrazoline antifoggant, said antifoggant being present in an amount sufiicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

17. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant, and an acetylene dicarboxylic acid antifoggant, said antifoggant present in an amount sufficient to increase the life of the developer at least 50% when com- 12 pared to the life of an identical developer stabilized with the surfactant.

18. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant and a degraded protein antifoggant selected from the group consisting of cysteine hydrochloride and histidine hydrochloride, said antifoggant being present in an amount sufficient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

19. A stabilized photographic physical developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to to metal, at least one ionic surfactant, and an antifoggant, selected from the group consisting of benzotriazole and S-methylbenzotriazole, said antifoggant being present in an amount suflicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

20. A stabilized photographic developer comprising an aqueous solution of a water soluble metal salt reducible to metal, a photographic reducing agent for reducing said metal salt to metal, at least one ionic surfactant, and at least one cyclic amine antifoggant, said antifoggant being present in an amount sufiicient to increase the life of the developer at least 50% when compared to the life of an identical developer stabilized with the surfactant.

References Cited UNITED STATES PATENTS 2,614,925 10/1952 Carroll et al. 9666 3,149,970 9/1964 Weyde 9648 3,157,502 11/1964 Jonker et a1. 9648 3,173,789 3/1965 King et al 9661 OTHER REFERENCES tember-October 1961, pp. 283-7.

NORMAN G. TORCHIN, Primary Examiner.

C. E. DAVIS, Assistant Examiner. 

